The U.S. military said it would transfer security responsibility for Anbar this week to the Iraqi military, a bellwether event that illustrates what Iraq and the United States describe as a profound stride in their efforts to foster stability.

Anbar is the 10th of the 18 provinces where Iraqi forces have taken charge of security control since the U.S.-led invasion in 2003 and the first largely Sunni Arab province to do so. The other provinces to take charge are in the Shiite south and the Kurdish north.

"We have seen a dramatic increase in security there," said Rear Adm. Patrick Driscoll, Multi-National Forces spokesman, speaking to reporters in Baghdad on Sunday.

"I think that the trend now in Anbar is to move from the violent kinetic to the rebuilding process," he said.

Anbar province -- west of Baghdad -- is a vast territory where Iraq shares borders with Syria, Jordan, and Saudi Arabia.

Much of the region is desert, and most of the people there live in in the towns and cities -- such as Falluja and Ramadi -- along the Euphrates River.

Sunni Arabs, such as those in Anbar, became politically marginalized when the Shiites and Kurds took over the new Iraqi government from the toppled Hussein regime, which had been dominated by and was most amenable to Sunnis.

Many Sunni Arabs in Anbar became active in the insurgency, and foreign fighters made their way into Anbar via Syria.

As a result, the Euphrates River valley region was a hotbed of insurgent activity in the early years of the Iraq war.